Big and dirty aluminum water tank!

[sailandbail]

I woke up this morning and decided today would be the day to tackle my old aluminum 80 gallon freshwater tank. I don't think it's ever been done. I cut some holes on each side of the tank with a jigsaw and to no surprise, it was pretty gnarly. Lots of deposits had formed on the bottom and sides. It's awkward to access the whole tank, so I just reached as far as I could with a scraper and got to work. The growth seems to chip off pretty easily, though I'm a bit worried that I will miss some spots mostly due to just not being able to reach or see everything.

Has anyone done this? Is there something that I can add to the tank that will combat these growths, which look like calcium deposits? I'm planning on cleaning it the best I can and then rinsing/pumping it out many times. I've read that adding bleach is beneficial. Are there products or chemicals that you would suggest adding on a regular basis, or even something more aggressive for cleaning?

When it's as clean as I can get it, what would you suggest I do to cover the new holes on the top of the tank? I was thinking about bolting down some plates so that I could remove it again in the future for maintenance. Any thoughts on that?


I really appreciate your time and advice. I love getting deep into projects like this. Thanks so much!!

Evan
37' 1979 Cooper Seabird

[a64pilot]

It is very likely lime deposits from hard water, just like you get on shower heads.
Bleach will react chemically and “eat” the aluminum, I avoid it like the plague for my aluminum tank and filter every drop that goes in through a carbon block filter.
I’d leave them be as they are most likely just hard water deposits, but physically removing them if you want to is likely to not do any harm.
I wouldn’t use any chemicals though.

How old is that tank?

[south4320]

ABYC standards don’t recommend aluminium for potable water tanks.
There have been studies in the past linking the use of aluminium pots etc to onset of dementia. I don’t know if that is still the case.
I worked in a small shipbuilding yard for a short time and saw a number of aluminium water tanks removed and cut open. They always contained a white sludge and I definitely wouldn’t use aluminium tanks for potable water.
I have been advised that the sludge was a result of a reaction from chlorine in treated water.

[wingless]

That aluminum tank could be sold for scrap metal and that money used to offset the cost of purchasing a translucent white plastic water tank.

[coopec43]

South4320 I would have agreed with you for exactly the same reasons you have stated: alzheimers. But apparently that hasn't been proven according to articles I have read earlier on today. I personally would prefer to steer clear of aluminum


Aluminum Water Tanks: Safe to Use? Potable water is best carried in stainless steel or FDA-approved, food-grade plastic tanks rather than in aluminum. Chlorine and aluminum are poor partners. ... Tanks made of 300-series stainless steel or FDA-approved plastic are far preferable.Aug 9, 2012
https://www.boats.com/reviews/aluminum-water-tanks-safe-to-use/


4.2 Water transport vehicle construction The water transport vehicle must be designed and constructed to prevent possible contamination of the water and must be able to be effectively cleaned. The vehicle must comply with the following:  Constructed of a suitable material (Food grade plastic, stainless steel, fibreglass, aluminium or coated mild steel)  All surfaces that may come in contact with drinking water must be made of a material that will not contaminate the water.
See AS/NZ4020: 2005 Testing of products for use in contact with drinking water


https://nt.gov.au/__data/assets/pdf_file/0011/208847/guidelines-for-drinking-water-transport-in-the-nt.pdf

[tkeithlu]

Bleach won't remove calcium carbonate deposits - both are bases. You need a mild acid to desolve calcium carbonate, white vinegar being the obvious choice. You can smell it, it foams carbon dioxide gas in reaction with the deposit, and it isn't toxic.

[GordMay]

Greetings and welcome aboard the CF, south.

Originally Posted by south4320

... There have been studies in the past linking the use of aluminium pots etc to onset of dementia. I don’t know if that is still the case...
... I definitely wouldn’t use aluminium tanks for potable water.
I have been advised that the sludge was a result of a reaction from chlorine in treated water.

No, that one study (from the 70's?) has long been discredited.

Like a64pilot, I wouldn’t use any chemicals.
CLR, for instance, will take the finish off of aluminum and copper.
➥ https://www.thecarycompany.com/facil...eaners/clr/faq

Likewise, be cautious when cleaning cast iron or aluminum with vinegar. If left too long, the acid could corrode the metal (cast iron and aluminum are reactive surfaces).

[a64pilot]

Originally Posted by tkeithlu

Bleach won't remove calcium carbonate deposits - both are bases. You need a mild acid to desolve calcium carbonate, white vinegar being the obvious choice. You can smell it, it foams carbon dioxide gas in reaction with the deposit, and it isn't toxic.

While vinegar isn’t toxic, I believe it’s reaction with the “lime” will result in salt water.
You need to clean out the vinegar and salt water. Assuming it’s “lime”
I put that in parenthesis as it’s likely calcium carbonate, but I’m not sure, people call it lime.
Anyway the lime isn’t harmful and could be argued it’s a beneficial mineral to have in your water.
What would be interesting is why does it seem to precipitate out in an aluminum tank, but not a plastic one?
Or shower heads for that matter.

[south4320]

Thank you for the welcome GordMay
I have no set opinion either way as to aluminium and Alzheimer’s but prefer to err on the side of caution.
I don’t know how to post links but if you look up
“Is there a link between aluminium and Alzheimers” you should find an article dated March 12 2018 by Yuko Haru Phd, Director of Ageing and Alzheimer’s Prevention at the Alzheimer’s Drug Discovery Foundation. According to that article some studies find a link other studies find no link and at present it seems we don’t have a definite answer.

[Bean Counter]

Depending on dimensions a bladder tank may be able to be inserted into the old tank. Connecting the inflow and outflow hoses might be a challenge.

[KP44]

I have an opinion to share:

There are several reasons to use aluminum for fuel tanks but never for fresh water.
If you have tasted tea or coffee from an aluminum container, you understand that aluminum reacts with water. Aluminum is a poisonous metal and concentrations of aluminum have been found in the brains of humans with dementia. Even aluminum cookware should be clad with steel to be safe for food.

[KP44]

Good time to consider a new tank.

[a64pilot]

Why would you want an aluminum fuel tank?
I have one, and wish it was plastic

[Ken Z]

I would replace tank with food grade plastic. Dont use bleach, it will corrode, also don t put bleach in your bilge it corrodes, can kill your bilge pump, corrode a keel stepped mast. Rubbing alcohol works to get mold out of water lines.

[coopec43]

I think if I was in your situation I would "play it safe" and coat the internal of the tank with a World Health Organization approved product suitable for potable water storage such as Crommelins Water Based Bitumen


FEATURES AND BENEFITS

• Excellent waterproof performance, remaining flexible and watertight in permanently wet conditions.
• Prevents damage, efflorescence, mould growth, staining and paint peeling associated with moisture transfer
• Economical, fast drying and easy to use.
  
• Suitable for permanent immersion.
• Suitable for the collection and storage of potable water

Testing Approvals: AS 4020: 2005 – Products for Use in Contact with Drinking Water


https://2ecffd01e1ab3e9383f0-07db7b9624bbdf022e3b5395236d5cf8.ssl.cf4.rackcdn.c om/Product/07e753f2-873b-4879-9a35-79af66fa699f.pdf